Microwave power combiners/dividers are used in different circuit applications. One such application is the combination of several incoming signals to achieve a coherent output signal having the desired output power. Conversely, an incoming signal may be divided to provide several output signals for digital signal processing devices.
Conventional combiners/dividers include a plurality of branches (fingers) coupled to a unitary terminal. When used as a divider, an input signal is supplied to the unitary terminal and is transmitted to the several branches. When used as a power combiner, several input signals are supplied simultaneously to the respective branches and combined to one output signal at the unitary terminal.
A well-known combiner/divider is the Wilkinson power divider. The Wilkinson device is conventionally used for binary dividing/combining; that is, successive divisions or multiplications by two. Hence, the Wilkinson device is limited in that the divisions or multiplications are always a factor of 2 and the input and output impedances are equal to characteristic impedance Z0. Regardless of its application as a combiner or a divider, the Wilkinson device does not allow different input/output impedances. Moreover, since the Wilkinson device uses quarter-wavelength line in each division/multiplication operation and is binary, each subsequent operation requires additional space for the additional quarter-wavelength lines. Most importantly, the Wilkinson device does not allow N-way combination or division response in dimensional circuits. Circuits may be categorized in four groups according to their dimensions: zero dimensional, one dimensional, two dimensional and three dimensional. For example, in two dimensional circuits, two dimensions of the circuit are comparable or larger than the wavelength of the corresponding frequency. The other dimension is much smaller than the wavelength; therefore, these circuits may be categorized as two dimensional or 2D.
Other conventional combiners/dividers provide multi-prong impedance transforming power devices having a first terminal (corresponding to a first transmission line) and N transmission line fingers. The transmission lines have first and second ends. At their second end, the transmission lines are coupled to the first terminal while at their second terminal they are positioned to electromagnetically communicate with a power source. When used as a combiner, power is provided to each of the transmission lines. When combined, the power from each transmission line is combined to form an output from the first terminal. A drawback of the multi-prong impedance is the failure to provide control of the impedance transformation functions over a broad band of frequencies, while simultaneously achieving a wide range of possible impedance transformations. That is, the multi-prong device is limited to providing substantially linear output/input.
Clearly, there is a need in the art for power combiner/divider apparatus that overcomes the shortcomings of the prior art.